High oil consumption/slow oil return to sump?

I can't seem to put my thoughts together on this so hoping people with more experience might be able to chime in: I just came back from a 1200 mile road trip in South Wales where I put my new to me 02 C4 cab through its paces. Before the trip I'd noticed the following two potential issues: - RMS is leaking (just a little bit) only when the car is sat for many days. After some forum sleuthing, this is normal/common and unlikely to be related to my woes. - Right hand side of the engine is covered in oil. Stupidly, I didn't clear it to monitor, BUT I've found a video from back in June, when I was surveying the underside and I've grabbed a still showing the then-minor leak. Does this look like it's coming from the variocam solenoid? I have an invoice from the PO for a VVT valve on bank 2 that was changed less than two years ago These two leaks left my electronic oil gauge around the halfway mark with the engine stone cold. While on the trip, the second day I really pushed the engine, redlining it and generally driving it through the Brecon Beacons the way it's meant to be driven. Engine sounded and drove gloriously. While filling up in the evening, I saw the oil gauge had dropped to below minimum and was flashing. I filled up with a full 1L of oil and monitored. Next day, same thing, high oil consumption/leak after pushing the car, the next morning was showing again as just below minimum when cold. This time filled up with 0.5L and stopped pushing the car. The following 1.5 days, including the long return to London, the car didn't consume a single drop of oil. The measurements were corroborated with the dipstick as well, although on occasion the dipstick said full and the electronic gauge said half full, depending on condition. In all cases I've found the time the electronic system allots to oil returning to the sump to be wildly underestimated. So what do I do now? The car is due a major service including sparkplugs soon, so I'm thinking this could be early evidence of scoring and I should get it scoped/pressure tested. On the other hand, I only have any oil consumption when really pushing the car, and tbh I don't know if it's consumption or a leak that happens under high load as I haven't seen any smoke come out the exhaust. Any ideas?

For a start ignore the dash dispstick, it works it out based on engine temp vs oil temp when last turned off and amount of time left since then. It tried to calculate how much oil 'should' have fallen back into the sump. It also presumes you are using a 0w40 oil, if you are not then it tells you.....well........f**k all. You have a dipstick, use it. What oil are you using? If using say a Mobil 1 0w50 then yeah, push the car for a couple of hours and get the oil hot and it will disappear. If you are using something like a Motul Sport 5w40 or Motul's 8100 X-Power 10w60 you probably won't use any oil for a good 1000 miles or more doing the same hard runs. Also, depends how hot the oil is when you pull in and stop for the night, pull over with it at 90ºc and it will give a completely different reading the following morning compared to if you pull in with it at 120ºc and much thinner. I did a couple of hundred miles at 70-80mph on the motorway on Friday night and on Saturday morning my oil was showing 1 bar (997 so only 3 bars of 400ml each and no dispstick). I only changed the oil 570 mile before and so thought I had used one bar in 570 miles, so around 1500 miles for a litre. But yesterday went out for a proper blast and when I parked up the oil was at 100ºc or more. Today when I got in the car it was back at 2 bar. Because the oil was hotter and therefore much thinner I just think more had run back into the sump. What oil are you using? How many miles has your car done? What is your oil pressure at idle when the car is fully up to temp? I can go through a litre in 900 miles or 4000 miles depending on ambient temps, how hard I am pushing the car and what oil I am using.

Car is on 91k miles. Oil pressure at ~1.7 bar. I haven't had it enough to do a service, it's actually due one and I'm having parts delivered this week. Previous service about a year ago was with Comma Syner-g 5w40. Unfortunate but it's only this last one (I think the PO mentally clocked out so cheaped out), it's been serviced with Mobil 1 0w40 the previous 5 years. When I had to top up I used what I found at the local petrol station, Porsche A40 approved 5w50 the first time (1L) and 10w40 the second (0.5L). Since I decided I'm doing the service work myself including plugs and coils (scary!) I'll have a look inside cylinder 6. It has "eaten" sparkplugs (oil fouling) so I'd be very surprised if I see absolutely 0 scoring. But I won't be doing a compression test unless I find it's badly scored as it's really asymptomatic at this point. Regarding the Variocam+ valves, I found a video showing you can change just the seal on them, actually it is the seal that has an issue going by a past invoice mentioning "oil leak around VVT bank 1 & 2" before the solenoid itself (not including the seal for some reason) crapped out, threw a code, and was changed by the PO. I ordered two of them from D911 for 10 quid each, should fix the oil leak in the photo above. So basically I've calmed down since the event, I'm fairly confident I can fix 1/2 leaks I can see (and well, can't really do much about the RMS leak for now, maybe if the clutch needs doing I sort it out) and we'll see about the liner condition. Car has been serviced regularly so maybe overkill, but I'll be doing Liqui Moly Engine Flush plus -> drain -> Millers Trident 5w40 (great price on opieoils) take her out on a run -> drain -> Millers 10w50. HOPEFULLY that might clear potential sludge that stop the oil from not doing what the electronic gauge thinks it's meant to do. But yeah when the car did not have enough oil it was showing on the dipstick as well. Now, will the thicker oil burden the AOS more? Potentially. But it seems there's no silver bullet.

Just a heads up, my car drinks Millers 10w50 NT+, like really gets through it. So don't panic if this don't slow consumption down. Shell Helix 5w40 is the best to reduce consumption I have tried so far... Shell Helix Ultra 5W40 5 Litre Engine Oil Shell Helix Ultra 5W40 5 Litre Engine Oil from the car parts & accessories specialists. Thousands of OEM & aftermarket products available interest free - shop now! www.arnoldclarkautoparts.com I got to 1800 miles and it hadn't dropped a bar on the electronic dipstick, but, when ambient temps got to 34ºc and oil temps hitting 110ºc my oil pressure hit 1 bar, so I swapped out for Motul Power 5w50. Back to 1.7 bar when oil at 95ºc and even at 105ºc it is still at 1.5 bar, which I feel happier with. I know Hartech say their rebuild with Millers drink a lot of oil too, but maybe if they swapped to something with a better HTHS rating and lower NOACK evap rates they might find their engines don't actually consume much at all?

I think their reason for using Millers is the very strong anti-wear additive package, as seen in a Project Farm video comparing it to Pennzoil Ultimate. Me, I mostly hope it stops the RMS leaking if the car sits for a while, and as for consumption, we'll see. It was rather extreme, ~1.2L consumed in 1200 miles sounds OK-ish, but in reality it was more like ~1L consumed in 200 miles that second day I pushed it. I still don't understand why I didn't notice or smell any smoke at all (the day had stops between activities). To rule out a leak, is there any system/area that might only leak under high RPM?

Your cylinders might be ovaled and can’t seal well at high RPM. My engine burns at the same rate (1L per 200-250 miles). I have yet to crack open the engine to check its roundness, but I have been driving like this for the last two years. It’s been so long that I have become quite used to it. I say you should drive on and keep feeding oil to the beast.

Blimey, what oil are you using radish?

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1 litre per 200-250 miles?! That is not normal…

I’m using Driven DI50, it’s a 15w-50 full synthetic. I’m in the US, by the way. I’m unsure whether you guys can find this oil. Yes, it absolutely is not normal, but it’s been like this for over a year now. It used to be at a rate of 1L per 400 miles, and steadily decreased over time. The current consumption rate will actually improve if I drive it like an old lady, though. It needs a rebuild, but finances are tight so I’m plodding on with it as-is. Considering I average about 15k miles per year, this engine is much stronger than I initially believed.

Mine started to gulp oil like that when I got bore score and eventually destroyed the rod bearings. Is one or both exhaust tips black? Any knocking or other unusual noises at idle? Does it smoke? A broken AOS may also cause this, and the pic you show doesn't appear to be the variocam solenoid. At least on the 3.4 the solenoids are at the end of the cam cover where there's a "bulge" for the cam chain. If it were a 3.4 I'd say your leak is from the spark plug tubes, but an 02 should not have them as it's a 996.2.

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It is the VVT, you can see it Different engine... that's one of the four variocam solenoids. So interim update: Did a full service today, plugs, coils + 2 valve solenoid seals on bank 2 + borescope inspection + normal service. 1. I have close to no bore scoring, there's only a quite minor scoring mark on cylinder 4, cylinder 6 was clean as a whistle. Very happy with this, I might post some pictures to have people with more expertise share their thoughts. 2. My idle RPM dropped to 650 after changing the plugs, previously was closer to 800. 3. Coils were done at some point only on bank 2? Strange. 4. All the plugs looked totally fine, even if they were due. 5. Quite a bit of carbon cleanup, I'll run a few fuel cleaners over the next few weeks to clean up the engine a bit. Importantly, all 4 of the variocam solenoids were leaking . Bank 2 camshaft actuator was changed in 2023 (had manufacturing date on it) yet they didn't changet the ~10 quid seal smh... I changed the two seals on bank 2 since that's what I had in hand, but I'm pretty sure it's the actuator housing itself that's leaking due to corrosion (oil inside plug). The prices for them are eyewatering (~250 x2 + 75-150 x2). I now understand why this was left untended by the PO. As long as they still work, I don't think I'll bother. Nothing prepared me for the ordeal it is to change coils and plugs on cylinder 5...What were they thinking with the exhaust hanger design... bank 1 is so much easier comparatively. Has anyone done walnut blasting on this engine and can comment on results and price paid?

I thought the same about exhaust hanger, I’m surprised no ones made a modified maybe 3 part affair you could disassemble for access ?

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Maybe because removing it is a major pain in the rear? Engine out job + heat torch + drilling/tapping

Yup, getting the original off in the first place is a job you don’t really want

My car is a 1999 C4 it’s done 200k and I change the oil every year or every 3000 miles. Last year I did 6 weeks touring Europe and 10 days up in the highlands doing the NC500. It drinks zero oil. The last couple of years I have started using Millers NT 10/50 oil. Oil pressure when hot at idle is just under 2bars, and goes up to 5 ish when taking it through the revs.